## 31 December 2017

### What is carnot cycle

The Carnot cycle is a thermodynamic cycle that can be invented by French Physicist Sadi Carnot in 1824.

## What is the Carnot cycle?

In the Carnot cycle, two reversible isothermal processes and two reversible adiabatic processes are done in a heat engine.

## Process of Carnot cycle :

The Carnot cycle consist of four processes following below :

• A reversible isothermal gas expansion process. From the diagram shown below the ideal gas in the system absorbs some amount of heat from the heat source at a high temperature and then expands thus the work was done on surroundings.
• A reversible adiabatic gas expansion process. In this process, the system is thermally insulated. The gas expands continuously and does work on surrounding, which causes the system to cool to a lower temperature.
• A reversible isothermal gas compression process. In this process, work has done surrounding gas and cause a loss of heat.
• A reversible adiabatic gas compression process. In this process, surrounding continue to do work to a gas, which causes the temperature to rise back to high temperature attain in the first process.

## The efficiency of the Carnot cycle :

It can be defined as the ratio of the energy output to the energy input. Here energy output is work done and energy input is heat addition.

From the calculation,

Q1 = Heat addition = R T1 ln v2 / v1

Wnet = R ln v2 / v1 (T1 – T2 )

Ŋcycle = Wnet / Q1  =  T1 – T2 / T1

The large back work is a big drawback of this cycle.

## Assumption of the Carnot cycle :

• No friction at all between the piston and cylinder and also other moving parts of the engine, thus there is no heat generated and lost due to friction.
• There is no transfer of heat with the external atmosphere because the engine is completely insulated.
• There is also no exchange of heat between various parts of the engine.